1. Field of the Invention
The present invention relates to a transmission rate control method for controlling transmission rate of an uplink user data, a mobile station, and a radio base station.
2. Description of the Related Art
In a conventional mobile communication system, in an uplink from a mobile station UE to a radio base station Node B, a radio network controller RNC is configured to determine a transmission rate of a dedicated channel, in consideration of radio resources of the radio base station Node B, an interference volume in an uplink, transmission power of the mobile station UE, transmission processing performance of the mobile station UE, a transmission rate required for an upper application, and the like, and to notify the determined transmission rate of the dedicated channel by a message of a layer-3 (Radio Resource Control Layer) to both of the mobile station UE and the radio base station Node B.
Here, the radio network controller RNC is provided at an upper level of the radio base station Node B, and is an apparatus configured to control the radio base station Node B and the mobile station UE.
In general, data communications often cause burst traffic compared with voice communications or TV communications. Therefore, it is preferable that a transmission rate of a channel used for the data communications is changed fast.
However, as shown in FIG. 1, the radio network controller RNC integrally controls a plurality of radio base stations Node B in general. Therefore, in the conventional mobile communication system, there has been a problem that it is difficult to perform fast control for changing of the transmission rate of channel (for example, per approximately 1 through 100 ms), due to processing load, processing delay, or the like.
In addition, in the conventional radio network controller RNC, there has been also a problem that costs for implementing an apparatus and for operating a network are substantially increased even if the fast control for changing of the transmission rate of the channel can be performed.
Therefore, in the conventional mobile communication system, control for changing of the transmission rate of the channel is generally performed on the order from a few hundred ms to a few seconds.
Accordingly, in the conventional mobile communication system, when burst data transmission is performed as shown in FIG. 2A, the data are transmitted by accepting low-speed, high-delay, and low-transmission efficiency as shown in FIG. 2B, or, as shown in FIG. 2C, by reserving radio resources for high-speed communications to accept that radio bandwidth resources in an unoccupied state and hardware resources in the radio base station Node B are wasted.
It should be noted that both of the above-described radio bandwidth resources and hardware resources are applied to the vertical radio resources in FIGS. 2B and 2C.
Therefore, the 3rd Generation Partnership Project (3GPP) and the 3rd Generation Partnership Project 2 (3GPP2), which are international standardization organizations of the third generation mobile communication system, have discussed a method for controlling radio resources at high speed in a layer-1 and a media access control (MAC) sub-layer (a layer-2) between the radio base station Node B and the mobile station UE, so as to utilize the radio resources effectively. Such discussions or discussed functions will be hereinafter referred to as “Enhanced Uplink (EUL)”.
As shown in a Non-Patent literature 1 (3GPP TSG-RAN TS25.309 v6.2.0), in a conventional mobile communication system using the “Enhanced Uplink”, the radio base station Node B is configured to transmit an “Absolute Grant Channel (AGCH)” which includes an absolute value for the transmission rate of uplink user data (an “Enhanced Dedicated Physical Data Channel (E-DPDCH)”) to each mobile station UE, so as to control the transmission rate of the uplink user data (i.e. the transmission rate of the E-DPDCH for transmitting uplink user data).
Each mobile station UE is configured to determine the transmission rate of the uplink user data (E-DPDCH) based on the absolute value included in the received AGCH.
Generally, if not otherwise specified, a radio base station means a cell in the radio base station, in the field of the Enhanced Uplink (EUL). In the field of the Enhanced Uplink (EUL), each mobile station UE is received the AGCH from a sieving cell of the mobile station UE.
Furthermore, generally, if not otherwise specified, a transmission rate includes a transport block size and a transmission power ratio (a ratio of an E-DPDCH transmission power to a DPCCH transmission power), in the field of the Enhanced Uplink (EUL). In addition, the AGCH includes a Radio Network Temporary Identity (RNTI).
Each mobile station UE is configured to determine whether or not the received AGCH is addressed for itself, using the Radio Network Temporary Identity (RNTI) included in the AGCH.
Further, as shown in a Non-Patent literature 2 (3GPP TSG-RAN R2-050438), there is a technique which enables a cell common transmission rate control which is common between cells and a mobile station individual transmission rate control which is individualized per mobile station UE, by having the plurality of Radio Network Temporary Identity (RNTI) at one mobile station UE.
Generally, in the mobile communication system using the “Enhanced Uplink”, it is required to set an effective period to the AGCH. However, the length of the effective period required by the cell common transmission rate control and the mobile station individual transmission rate control is different.
Generally, in the field of the Enhanced Uplink (EUL), the effective period can be set by using a elapse time since the AGCH is received (for example, 10 ms, 5 TTI (Transmission Time interval) or the like).
In the field of the Enhanced Uplink (EUL), the effective period can be seen to set per HARQ process, as each HARQ process corresponds to a time interval or TTI (Transmission Time Interval). In the example of FIG. 14, the HARQ processes #4 to #8 are set as the effective period of the AGCH.
The effective period to the AGCH, which includes a Radio Network Temporary Identity (RNTI) for the cell common transmission rate control, is short.
Therefore, there has been a problem that when the specific one effective period to the AGCH is determined for both of the cell common transmission rate control and the mobile station individual transmission rate control, it is required to transmit the AGCH at frequent intervals, and the radio capacity in the downlink is decreased.
In addition, the effective period to the AGCH, which includes a Radio Network Temporary Identity (RTNI) for the mobile station individual transmission rate control, is long.
Therefore, there has been a problem that when the specific one effective period to the AGCH is determined for both of the cell common transmission rate control and the mobile station individual transmission rate control, it is not possible to allocate the transmission to each mobile station UE in fast, the scheduling becomes low speed, and the transmitting efficiency (throughput) in uplink is decreased.